Active walls

ABSTRACT

A powder distribution device for transporting and mixing a fine powder with a gas is disclosed. The device presents a distribution member forming a connection between a source of fine powder and a discharge opening. The distribution member has a first inlet portion ( 10 ) and an outlet portion ( 12 ) for a stream of a first gas ( 1 ) mixed with the fine powder. The main body of the distribution member constitutes a porous body portion ( 16 ) being surrounded by a second gas ( 2 ). If a pressure gradient is created between the second gas ( 2 ) and the first gas ( 1 ), i.e. the first gas ( 1 ) being at a slightly lower pressure, the second gas ( 2 ) will leak trough the porous body ( 16 ) and thereby preventing powder, in the mix of the first gas and fine powder, from sticking or clogging within the distribution member, which thereby forms an active non-sticking wall relative to of the fine powder.

This application is a division of application Ser. No. 09/665,064, filedon Sep. 19, 2000, now U.S. Pat. No. 6,536,426, the entire contents ofwhich are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a method and a device for minimizingthe amount of a fine powder sticking to the walls of a distributionmember carrying a mix of air and the powder.

BACKGROUND

Within some technical areas there is a problem in that some part of afine powder mixed with a gas and subsequently transported by this gas,e.g. air, will stick to the walls of a distribution member when itpasses through this distribution member. Instruments for measuring forinstance the amount of powder mixed with a transporting gas as well asproviding a measure of the grain size distribution often faces theproblem that the different sizes powder grains to be measured willeasily stick to the walls of a measurement channel. This implies thatcleaning must be regularly performed when measuring, besides theaccuracy of the measurement will be very dependent of how often measuresfor cleaning will be performed.

Another area facing a similar problem, for instance, is theadministering of medical compositions by means of inhalers.Administering of medical powders today can be performed in numerousways. Within health care more and more is focussed on the possibility ofdosing medical drugs as a powder directly to the lungs of a patient bymeans of an inhaler to thereby obtain an effective, quick andpatient-friendly administering of such substances.

For the medical powders, being administered by means of an inhaler, toland in the lungs, the powder should preferably have a grain size of 0.5to 10 μm. A larger grain size will easily be sticking just in the mouthand throat, and a smaller grain size may accompany the expiration airout again.

Small grain size powder also has a strong tendency of agglomerating,i.e. to get conglomerated. In the inhalers, which are used today, alarge extent of the active substance is in the form of agglomerates whenit is dosed and much powder therefore will stick in the upperrespiratory tract. Different ways to de-agglomerate the powder have beendeveloped and in most cases the inhalation air is utilized fordecomposing the agglomerates.

It is also common to use carriers having a larger grain size onto whichthe fine powder is distributed. Upon inspiration the large grains willthen stick in the oral cavity while the small grains are set free andproceed to the lungs. Certain manufacturers also use electrically drivenpropellers, piezo-vibrators and/or mechanical vibration to decompose theagglomerates. Thus, achieving a very large portion of individualparticles in the inspiratory air is a very important factor forobtaining a high degree of effectiveness upon inhalation. Yet anotherproblem is that the medical composition powder also will stick to thewalls of an inhaler distribution member normally connected to a suitablemouthpiece for the administration by means of an inspiration.

Therefore there is a demand of a solution which will to a large extentprevent particularly fine powder or its agglomerates from sticking to adistribution member, for instance, in a measuring instrument or aninhaler, which otherwise may be more or less clogged due to powdersticking to its walls.

SUMMARY

A powder distribution device for transporting and mixing of a finepowder with a gas is disclosed. The device presents a distributionmember forming a connection between a source of fine powder and adischarge opening. The distribution member has a first inlet portion andan outlet portion for a stream of a first gas mixed with the finepowder. The main body of the distribution member constitutes a porousbody portion being surrounded by a second gas. If a pressure gradient iscreated between the second gas and the first gas, i.e. the first gasbeing at a slightly lower pressure, the second gas will leak trough theporous body and thereby preventing powder, in the mix of the first gasand fine powder, from sticking or clogging within the distributionmember, which thereby obtains an active non-sticking wall relative to ofthe fine powder.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further objects and advantages thereof, maybest be understood by making reference to the following descriptiontaken together with the accompanying drawings, in which:

FIG. 1 illustrates a distribution member according to the presentinvention for connection to a source of fine powder, and

FIG. 2 illustrates a further embodiment of a distribution memberaccording to the present invention to regulate the amount of the secondgas to obtain a desired pressure gradient.

DETAILED DESCRIPTION

In FIG. 1 is presented an embodiment of a distribution memberillustrating the present invention. Such a distribution member may beused, for instance, in a measuring instrument or may even be utilized inan inhaler device. In a measurement instrument the distribution memberwill be inserted between a source delivering a powder to be mixed with agas transporting the powder for forming a measurement set-up. Aninstrument utilizing the distribution member could typically be ameasurement set-up for measuring the size of the powder particles fromthe powder source as well as the distribution of particle sizes whentransported by a gas flow. A typical such measurement for instance mayutilize a laser beam, which will be scattered by the small grains ofpowder transported by the gas. In an inhaler the distribution member maybe inserted between a source of powder and a mouthpiece used for theinspiration of powder.

An input side 10 of the distribution member is connected to a suitablepowder source. Similarly an output side 12 of the distribution member isconnected to an exhaust, which in the case of an inhaler would be asuitable mouthpiece for the inhalation. The main distribution member inan illustrative embodiment consists of, for instance, a tube having aporous body 16. A first gas 1 passing through the distribution memberbody contains a mixture of gas and powder, for instance a medicalcomposition to be administered by means of an inhaler. The distributionmember according to a first embodiment demonstrated in FIG. 1 issurrounded by a second gas 2. A pressure difference between the firstgas 1 and the second gas 2 is normally obtained by creating anunder-pressure in the first gas 1, for instance, by a suction of thefirst gas 1 from the outlet portion 12. When the second gas 2 is at ahigher pressure compared to the first gas 1 the second gas 2 will leaktrough the porous body portion 16 then preventing powder from stickingor clogging at the inner of the distribution member body.

In a second illustrative embodiment, for obtaining a desired pressuregradient, a second gas 2 is fed via a second inlet 14 in a second wall15 into a space between the porous body 16 and the second wall 15. Byregulating the amount of the second gas a desired pressure gradient willbe obtained. The gas-flow passing through the distribution member willcontain a mixture of the first gas 1 and a powder. This gas-flow thenstill presenting a lower pressure compared to the second gas 2 impliesthat the second gas 2 will leak through the porous body 16 and preventpowder from sticking to the inner wall of the porous body 16. A typicalgas to be used in a measurement set-up will be air or in some set-upsdry air, but any other type of available gas may be used, for instance,even an inert gas may be used. A typical material for the distributionmember body 16 is sintered porous plastic, but also porous sinteredmetal may be used. Preferably the material is conductive orelectrostatic dissipative and connected to a device ground to preventelectrostatic charging. By balancing the pressure at the second gasinlet 14 against the pressure of the transportation gas 1, the secondgas 2 when leaking through the porous body will also assist in furtherdistributing the powder within the first gas 1. This is also valid in aninhaler device utilizing the present distribution member for improvingthe efficiency of the inhaler in which the pressure gradient is createdby the suction of the first gas 1, in this case just ordinary air, wheninhaling a medical composition powder mixed with air. In a furtherembodiment of an inhaler the entire portion of the inhaler case incontact with the powder to be administered may be formed of a porousmaterial preferably enclosed in an outer shell. This outer shell thenforming a space between an outer wall 15 and the inner porous body forobtaining a pressure gradient towards the interior of the devicethereby, by means of the porous inner body 16, preventing powder grainsfrom sticking to the inner body of the inhaler device.

It will be understood by those skilled in the art that variousmodifications and changes may be made to the present invention withoutdeparture from the scope thereof, which is defined by the appendedclaims.

What is claimed:
 1. A powder distribution device for transporting andmixing of powder with a gas comprising a distribution member bodyforming a connection between a source of fine powder and a dischargeopening, whereby the distribution member body comprises a porous bodyhaving a first inlet portion and an outlet portion for a stream of afirst gas mixed with the fine powder, the porous body being surroundedby a second gas, which when creating a positive pressure gradientbetween outer and inner regions of said distribution member body thesurrounding second gas will leak through the porous body of thedistribution member body, thereby preventing powder particles fromsticking to the inside of the distribution member.
 2. The deviceaccording to claim 1, wherein said porous body of the powderdistribution device is made from sintered porous plastic or a poroussintered metallic material.
 3. The device according to claim 2, whereinsaid porous body is conductive or electrostatic dissipative andconnected to a device ground to prevent electrostatic charging.
 4. Thedevice according to claim 1, wherein said first gas and said second gasboth constitute air.
 5. The device according to claim 1, wherein apressure difference between said first gas and said second gas isobtained by creating an under-pressure in said first gas by a suction ofthe first gas from said outlet portion.
 6. The device according to claim1, wherein the powder distribution device further constitutes an outerwall portion encircling the inner porous body and said outer wallportion further being provided with a second inlet portion for an inletof said second gas at a higher pressure compared to said first gas tohave the second gas leak through said inner porous body portion therebypreventing powder from sticking or clogging at inner walls of thedistribution member.
 7. The device according to claim 5, wherein apressure difference between said first gas and said second gas isobtained by adjusting the pressure of said second gas fed at said secondinlet portion.
 8. The device according to claim 1, wherein the powderdistribution member at its first inlet portion also constitutes a sourceof powder to thereby form an inhaler arrangement connected to amouthpiece for inhaling the powder, whereby due to active inner walls ofthe device powder will not stick to inner walls of the inhaler.